In various mechanical systems, in order to evaluate the performance and reliability of a structure, it is indispensable to measure vibration properties. For example, it is necessary to perform measurement of vibration properties in vibration measurement of information equipment (head actuator mechanism of hard disk drives (HDD) or the like), MEMS (Micro Electro Mechanical Systems), or the like, and actual operation of large-sized equipment (cars or the like).
In recent years, MEMS that is a device that is produced using semiconductor ultra-fine processing technology or the like and has versatile functions integrated therein has attracted attention. For example, a MEMS device is mounted on an accelerometer, a pressure sensor, an air flow sensor, and the like as various sensors for cars or medical applications. As various sensors and actuators using the MEMS technology are developed from now on, development for application to optical communication and mobile equipment, application to peripheral devices of a computer, and application to bio-analysis and portable power sources is expected.
On the other hand, the MEMS device has a fine structure and the technology of inspecting the device properly is also important. For this reason, high-precision vibration measurement technology in a broad frequency band/high-frequency band is required.
In order to measure the vibration properties of a structure, FRF is obtained by applying an impulse input (for example, impulse excitation force) to the structure and measuring an input and an output. The methods that have become generally widespread for applying the impulse input to the structure are a method of attaching an excitation machine or the like separately and applying an impulse excitation force in a contact manner, a method of performing striking using an impulse hammer, and the like.
In measurement of the vibration properties of the structure, an input sensor and an output sensor are arranged in contact with the structure in order to measure the input and output when the impulse input is applied to the structure. A load cell is included in examples of the input sensor. An accelerometer is included in examples of the output sensor. Additionally, non-contact type sensors, such as a laser Doppler vibrometer and a laser displacement gage, are also included in examples of the output sensor.
In recent years, in order to apply the impulse input (impulse excitation force) to the structure, irradiating the structure with a laser beam and generating ablation have also been suggested (refer to NPL 1). According to impulse excitation using ablation, an excitation force in a high-frequency band can be applied to the structure. However, even in the method reported in NPL 1, it is necessary to arrange an input sensor for measuring the impulse excitation force in the structure.